I've had this installed on my '91 since 1998. The brace helped
significantly for chassis rigidity, and keeps vibrations to a minimum. My car
is driven into the city daily, and the brace does a nice job of helping to settle
the car after a hard bump. Steering response was also slightly improved. Definitely
a "must have" for the early M1's. Not sure how noticable it will be
on the stiffer M2's (where applicable).

This is a very sturdy piece that appears to have been CNC machined
from a 1/4" thick piece of sheet aluminum. It comes powdercoated black.
Overall quality A+. Installation is pretty straightforward, but make sure to
spray the mounting bolts prior to removal. This unit has a removable section
on the top portion, so there's no need to remove the exhaust. You may want to
use some anti-seize compound on the 4 bolts that hold in the removable section
just for future maintenance to the exhaust. The downside is that whenever you
need to remove the brace (for maintenance, new sway bars, etc.), you have to
disturb the lower A-arm bolts, which can throw off your alignment, so make sure
you mark their positions before moving them.

Ties the rear subframe together with four mounting points.
Applicable to '90-'91 and '99+

This is a nicely engineered product with a seperation that
allows installation without removal of the exhaust system. The instructions
were very clear and easy to follow. As I have '90 that's been winter driven,
before installation, I spayed the bolts to be removed with liberal amounts of
WD40 a couple days in a row. Even with the extra care I took to brush the rust
off the threads, and easing off the bolts to prevent breakage, the whole procedure
can be done in less than 2 hours. However, when I was tightening the last sway
bar bolt using my torque wrench, the damn bolt snapped on me.. so 2 hours of
dremel'ing and drilling out the stud later everything was done.

Things feel a little tighter with brace, but I haven't taken
it on the highway yet, so that may yield a greater effect. I have a front brace
on order that should further firm things up.

I installed the cannon brace along with replacing the sway
bar bushings. It took a couple of hours so you don't have to worry about any
significant Miata downtime. The instructions that came with it was very clear
and easy to follow. The only part not specified specifically that should be
is the direction of the 4 bolts that encloses the brace around the tailpipe.
I can't remember which way they face so email me and I'll check under the car
prior to replying. They helped a little with ride quality but not as noticeable
a improvement than the improvements by installing the front chassis and rear
bulkhead brace. I don't know what I'd say if the braces were installed in reverse.

If you own an pre 94 miata without braces, GO OUT AND GET
SOME! For a few hours work, you will love driving your Miata even more. I'd
wish someone can come up with a brace that ties the control arm forks together.
The newer Miatas have them because they rotated the control arm bolts 90 degrees.
Someone at the magazine should write a comprehensive chassis comparison that
clears the fog once and for all..